This invention relates to a connecting rod including a spherical surface portion, a rod portion and a pad portion for a radial piston motor suitable for use with watercraft, concrete mixers, etc., and a method of producing same.
This type of connecting rod has hitherto been produced, as shown in FIG. 1, by first forming a spherical surface portion 1, a rod portion 2 and a pad portion 3 having a sliding surface 5 integrally with one another (to provide a blank 4) as by a lost-wax precision casting process, and then applying a lining of white metal bearing alloy to the sliding surface 5 (of arcuate shape as shown in FIG. 3 et seq.) of the pad portion 3 by pouring molten alloy thereon. Owing to the complex shape of the connecting rod, a casting process used for applying a white metal bearing alloy becomes complex in construction, thereby increasing cost and making it difficult to obtain a bearing alloy of highly compact and uniform structure because difficulties are encountered in effecting uniform cooling which is one of the conditions for casting that should be met. Thus a bearing alloy having a lining applied thereto by pouring molten alloy, such as molten white metal bearing alloy, on the sliding surface of the pad portion has tended to have segregated thereon acicular crystals (Cu.sub.6 Sn.sub.5) and cubic crystals (SnSn), which are hard and brittle intermetallic compounds, and to have coarse crystals formed thereon.
Before and after the blank 4 has a lining applied to the sliding surface 5 of the pad portion 3 by pouring molten alloy thereon, the blank is machined individually to have its inner diameter finished. This has made it necessary to use a machining and holding device of a complex shape. Thus the time required for machining such workpiece has been long and no stability has ever been obtained in the precision with which the workpiece is finished. When an overlay is applied to the bearing alloy as required, each workpiece has to be treated individually, and this has made it necessary to use a expensive device of complex construction and perform a time-consuming operation. Yet it has hitherto been difficult to provide an overlay of uniform thickness.